1. Field of the Invention
This invention relates to a device and method for measuring vertical load that is at least partially supported by an axle of a vehicle such as a railroad car.
2. Description of the Related Art
In the railroad industry, it is frequently desirable to know the weight of a railroad car, and the load supported by each axle of the railroad car. For instance, in the railroad industry, the cost of a shipment may be based on the weight of the shipment. Thus, to ascertain accurate shipment charges, accurate weight of the shipment is required.
In addition, it is also advantageous to know the load of vehicles such as railroad cars because load limits of these vehicles are often exceeded. Overloading of a railcar can detract from the safety of the railcar since various components of the railcar, such as the axles, have limits to the load they can safely support. If the load supported by an axle is too great, the axle may become damaged or even catastrophically fail. Similar risks exist for other components in the load bearing system of a railroad car.
There are known devices for measuring the load of various vehicles such as tractor-trailers. One known method for measuring a load is to measure the strain on the load bearing components that is caused by the load. In particular, measured strain on the load bearing member varies depending on the load applied to the load bearing member. This measured strain can then be converted into a correlated load value to thereby provided a measured load that is supported by the load bearing member.
For example, U.S. Pat. No. 6,118,083 to Boyovich et al. discloses a weight measurement apparatus for determining the weight of a load supported by the axles of a tractor-trailer. A load bearing member, such as a trunnion member, is coupled between a portion of the suspension of the tractor-trailer. The weight measurement apparatus disclosed includes a plurality of strain gauges that are positioned in the trunnion member such that they straddle the principle stress axis of the trunnion member. The measured strain is then converted into a correlated load measurement that is supported by the trunnion member.
However, Boyovich et al. does not disclose a load measurement device which measures the load on an axle of a railcar, or a load measurement device that can be modified for such application. The suspension components of a railcar is significantly different than the suspension components of a tractor-trailer so that the device of Boyovich et al. cannot be readily implemented in a railcar. In particular, the invention disclosed in Boyovich et al. requires a specially designed trunnion member which is integral to the suspension of the tractor-trailer, but generally not utilized in railcars. In addition, provision and fitting of such a trunnion member is expensive and thus, cannot be easily and cost effectively implemented in tractor-trailers already in service, much less in railcars having a substantially different suspension.
Therefore, there exists an unfulfilled need for an improved load measurement device that is adapted to measure the vertical load on an axle of a railroad car. In particular, there still exists an unfulfilled need for such a load measurement device that is economical to implement.